Intraoral x-ray sensor with embedded standard computer interface

ABSTRACT

An intraoral x-ray sensor including a sensor housing and a universal serial bus (USB) data cable. The sensor housing has an opening. The USB data cable includes an outer sheath and a first data line, a second data line, a ground line, a power line, and at least two independent fillers positioned within the outer sheath. In one embodiment, at least two lines selected from the group including the first data line, the second data line, the ground line, and the power line are twisted together to form a single bundle. The opening receives the data cable.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S.application Ser. No. 13/611,572 (the “'572 Application”), filed on Sep.12, 2012. The '572 Application is a continuation application of U.S.application Ser. No. 12/796,251 (the “'251 Application”), filed on Jun.8, 2010, the entire contents of which is hereby incorporated byreference. The '251 Application claims priority to U.S. ProvisionalPatent Application Ser. No. 61/226,556, filed Jul. 17, 2009, the entirecontents of which is hereby incorporated by reference. This applicationis also related to U.S. patent application Ser. No. 12/605,624, filedOct. 26, 2009, U.S. Provisional Patent Application Ser. No. 61/108,552,filed Oct. 27, 2008, and U.S. Provisional Patent Application Ser. No.61/226,533, filed Jul. 17, 2009, the entire contents of which are herebyincorporated by reference.

BACKGROUND

The present invention relates to x-ray imaging, including dental x-rayimaging. More particularly, embodiments of the invention relate to adata transfer cable for an intraoral sensor with improved mechanicalstrength and heat transfer properties

X-rays have been used in dentistry to image teeth and parts of the mouthfor many years. In general, the process involves generating x-rays anddirecting the x-rays at the patient's mouth. The x-rays are attenuateddifferently by different parts of the mouth (e.g., bone versus tissue)and this difference in attenuation is used to create an image, such ason film or by using electronic image sensor.

SUMMARY

One challenge associated with electronic intraoral x-ray systems relatesto the mechanical stress on a cable coupling the sensor capturing imagesand an output device, such as a computer. To capture dental x-rayimages, the intraoral sensor is positioned within the oral cavity ofeach patient, which often includes twisting and tugging forces beingexerted on the cable. The repeated and continuous positioning of theintraoral sensor for each patient results in increased mechanicalstress, which wears the cable. With increased use and wear, the cablecan malfunction and become unusable.

An additional challenge relates to the environment in which theintraoral sensor operates: the oral cavity of a patient. The electronicswithin the intraoral sensor generate heat and, if left unchecked, canresult in injury to the patient. Certain governmental regulations orother standards apply to devices, such as intraoral sensors, that limitthe maximum operating temperature. For instance, safety standard 60601-12^(nd) edition from the International Electrotechnical Commission (IEC)limits the outside temperature of such intraoral sensors to 41 degreesCelsius.

In one embodiment, the invention provides, among other things, anintraoral x-ray sensor including a sensor housing and a universal serialbus (USB) data cable. The sensor housing has an opening. The USB datacable includes an outer sheath and a first data line, a second dataline, a ground line, a power line, and at least two independent fillerspositioned within the outer sheath. At least two lines of the first dataline, the second data line, the ground line, and the power line aretwisted together to form a single bundle. The opening is configured toreceive the data cable.

Additionally, some embodiments of the invention provide, among otherthings, an intraoral sensor including a sensor housing having a topportion and a bottom portion. The sensor further includes a twisted-quaduniversal serial bus (USB) cable coupled to the top portion. Thetwisted-quad USB cable includes an outer sheath and, within the outersheath, a first data line, a second data line, a ground line, a powerline, and four fillers that are twisted together to form a singlebundle. The sensor also includes circuitry within the sensor housing.The circuitry converts x-rays received through the bottom portion intox-ray data and outputs the x-ray data along the twisted-quad USB cable.

In some embodiments, the first data line, the second data line, theground line, the power line, and the four fillers are symmetricallyorganized about a centerline of the twisted-quad USB cable.Additionally, in some embodiments, the four fillers includes a firstfiller, a second filler, a third filler, and a fourth filler. The firstfiller abuts the ground line and the first data line; the second fillerabuts the ground line and the second data line; the third filler abutsthe power line and the first data line; and the fourth filler abuts thepower line and the second data line. In some embodiments, the fourfillers are made of a plastic, electrically insulating material.

In some embodiments, the outer sheath includes a braided shield and iscoupled via a heat-conducting wire to a metallic layer substantiallycovering an inner surface of the top portion. In some embodiments, theouter sheath further comprises a jacket layer outside of the braidedshield and a tape layer inside of the braided shield. Additionally, insome embodiments, the sensor includes an isolation layer within thesensor housing. The isolation layer is between the circuitry and the topportion and wherein the isolation layer is electrically insulating andheat conducting. In some embodiments, the isolation layer is coupled toone of the metallic layer and the braided shield via one of a secondheat-conducting wire and direct contact to provide heat transfer fromwithin the sensor housing to the twisted-quad USB cable.

Additionally, embodiments of the invention provide an intraoral x-raysensor including a housing and circuitry within the housing. The housingincludes a top portion and a bottom portion. The top portion has a firstinner surface and a first thermal resistance. The first inner surface issubstantially covered by a metallic layer with a second thermalresistance that is lower than the first thermal resistance. Thecircuitry converts x-rays received through the bottom portion into x-raydata and outputs the x-ray data along a data cable. The data cableincludes wires within a metallic shield. The metallic shield is coupledto the metallic layer by a thermally conductive path that has a thermalresistance that is less than the thermal resistance of air.

In some embodiments, the bottom portion includes a second inner surfacesubstantially covered by a second metallic layer that is coupled to themetallic layer either directly or via another thermally conductive path.The circuitry is contained on a printed circuit board (PCB) that isisolated from the metallic layer by an isolation layer. The isolationlayer is thermally conductive and electrically insulating, and includes(in some implementations) an opening through which the circuitry and thewires are connected. Additionally, in some embodiments, the circuitryincludes an array of pixels on a first side of the PCB and, on a secondside of the PCB, a processor and an input/output module. The sensorincludes x-ray attenuation components between the second side and asurface of the bottom portion through which x-rays are received. Thex-ray attenuation components may include: a lead layer, a fiber opticcovered by a scintillating layer, and copper planes. The top portionincludes a dome (with the shape of a partial, elliptical paraboloid)having a face with a circular opening. The circular opening receives thedata cable.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a dental x-ray system including anx-ray source, an intraoral sensor located in a patient's mouth, and acomputer connected to the intraoral sensor.

FIG. 1a is a schematic illustration of the intraoral sensor shown inFIG. 1 showing internal components of the sensor.

FIG. 2 depicts an exploded view of the intraoral sensor shown in FIG. 1.

FIG. 3 depicts a cross section along line A of FIG. 4.

FIG. 4 depicts a top view of the intraoral sensor shown in FIG. 1 and acable connector.

FIG. 5a depicts a cross section of a prior-art universal serial bus(USB) cable.

FIG. 5b depicts a wiring diagram of a prior-art universal serial bus(USB) cable.

FIG. 6a depicts a cross section of a cable according to embodiments ofthe invention.

FIG. 6b depicts a wiring diagram of a cable according to embodiments ofthe invention.

FIG. 7 depicts the underside of the top cover of the intraoral sensor ofFIG. 1.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

FIG. 1 illustrates a dental x-ray system 10. The system includes anx-ray source 12. In the embodiment shown, the source is located on anend 13 of a mechanical arm 15. When activated, the x-ray source 12generates an x-ray stream 16 that has a generally circularcross-section. (Of course, x-rays are generally invisible, but arepresentation of a stream is illustrated to facilitate understanding ofthe invention.) In many applications, a collimator is used to reduce thesize of the stream and generate a smaller x-ray stream having arectangular cross-section. A collimator may be used with a mechanicalpositioning device to help align the x-ray stream with an x-ray sensor.As shown in FIG. 1, x-ray source 12 is positioned (e.g., by an operator)so that the x-ray stream 16 is directed to an intraoral sensor 20. Theintraoral sensor 20 is shown located in the mouth of a patient 21. Insome embodiments, the intraoral sensor 20 includes a scintillator thatcoverts x-ray radiation to visible light. In other embodiments, thesensor 20 is configured to convert x-rays into electric charge without ascintillator. Unless otherwise specified, the term pixel refers both toa pixel in the array of pixels that converts x-rays to electrons withouta scintillator and a pixel in the array of pixels and its associatedscintillator or portion of a scintillator.

As best seen by reference to FIG. 1a , the sensor 20 also includes anarray of pixels 22. The components of FIG. 1a , including the array ofpixels 22, are not drawn to scale relative to the outline of the sensor20. Each pixel produces an electric signal in response to light (fromthe scintillator) or x-ray radiation impinged upon it. In oneembodiment, the sensor 20 includes one or more “on-board”analog-to-digital converters to covert analog signals generated by thepixels to digital signals. These signals are provided to a processor 23(such as a programmable, electronic microprocessor, field programmablegate array, erasable programmable logic device(s), or similardevice(s)). In the embodiment shown, the processor 23 is connected tomemory 24 (ROM and RAM) and an input-output interface 25. The sensor 20also includes one or more electronic circuits for power supply, drivingthe array of pixels, and driving the output (e.g., circuits located inthe I/O interface 25). In some embodiments, the I/O interface 25 is auniversal serial bus (“USB”) interface.

In some embodiments, the processor 23 controls image capture ortriggering of the sensor 20. In other embodiments, the x-ray source 12is coupled to the sensor 20, e.g., via computer 30, such that when thex-ray source 12 is activated, a command is sent (simultaneously ornearly simultaneously) to the sensor 20 to perform an image capture.Thus, it is possible to generate a burst of x-ray radiation and beassured that an image will be captured by the sensor 20 during therelatively short period of x-ray exposure either through automatictriggering or via a specific capture command sent to the intraoralsensor 20.

Referring back to FIG. 1, a wire, cable, or similar connector 27 of thesensor 20 connects the sensor 20 to a computer 30. The computer 30includes various components, including a processor or similar electronicdevice 32, an input/output interface 34, and memory 36 (e.g., RAM andROM). In some embodiments, the input/output interface 34 is a USBconnection and the cable 27 is a USB cable. FIG. 1 illustrates thatimage data captured by the sensor 20 and processed by the computer 30 issent to a display 38 and viewed as image 40. (Image 40 is drawn moredistinctly than an x-ray image would typically appear.)

The location of the intraoral sensor 20 in the patient's mouthdetermines what part of the patient's anatomy can be imaged (e.g., theupper jaw versus the lower jaw or the incisors versus the molars.) Anx-ray operator places (or assists the patient in placing) the intraoralsensor 20 at a desired location with the patient's mouth. Various sensorholders (including those that are used with or that include acollimator) may be used to keep the sensor 20 in the desired locationuntil an image is created or captured. For example, some holders aredesigned so that the patient bites the holder with his or her teeth andmaintain the position of the sensor 20 by maintaining a bite on theholder. After the sensor 20 is positioned behind the desired anatomicalstructure, and the x-ray field to be generated by the x-ray source 12 isaligned with the sensor 20, it is possible that the source 12 and sensor20 will, nevertheless, become misaligned. Misalignment can be caused bythe patient moving his or her head, moving the intraoral sensor 20 (byre-biting the holder, moving his or her tongue, etc.), and other causes.

FIG. 2 depicts an exploded view of the intraoral sensor 20. The sensor20 includes a housing 45. The housing 45 has a top portion 50 and abottom portion 55. Within the housing 45 is an insulator 60, a printedcircuit board (“PCB”) 65, a silicon detecting layer 67, an x-rayconverter 70, and a cushioning layer 71, which protects againstmechanical shocks. Some embodiments of the sensor 20 do not include thecushioning layer 71.

The top portion 50 includes a dome 75 that receives cable 27. The dome75 has a shape that approximates an elliptical paraboloid divided inhalf by the surface 76 of the top portion 50 (a partial, ellipticalparaboloid shape). Other dome shapes are contemplated for use inembodiments of the invention. The dome 75 includes a face with anapproximately circular opening through which the cable 27 passes. Thecable 27 includes connectors (e.g., wires), a portion of which passthrough an opening 79 of the insulator 60 to connect to the PCB 65. Insome embodiments, a ribbon or other connector passes through the opening79 to couple the wires of cable 27 to the PCB 65. The insulator 60provide electrical isolation between the PCB 65 and the housing 45 ofthe sensor 20. In some embodiments, the insulator 60 also secures thePCB 65 and x-ray converter 70 in position and protects each againstmechanical shocks. Although the insulator 60 resists conductingelectricity it is a conductor of heat, which assists in transferringheat away from the PCB 65.

The PCB 65, silicon detecting layer 67, and converter 70 include thecomponents of the sensor 20 illustrated in FIG. 1a , namely the array ofpixels 22, the processor 23, the memory 24, and I/O interface 25. In theembodiment depicted in FIG. 2, the array of pixels 22 includes aplurality of pixels, each pixel including a converting portion (i.e., aportion of converter 70) and a detecting portion (i.e., a portion ofsilicon detecting layer 67). The PCB 65 supports the silicon detectinglayer 67 (e.g., a CMOS die) and converter 70, with the silicon detectinglayer 67 being secured, e.g., using a glue or epoxy, to the PCB 65. Theconverter 70 converts x-rays received through the bottom portion 55 intolight. The light travels to the silicon detecting layer 67, whichconverts the received light into charge. The charge is integrated ateach pixel and the quantity of charge integrated represents the amountof x-rays received (although some of the integrated charge isattributable to noise and dark current). During a read-out of the arrayof pixels 22, the processor 23 determines the quantity of chargeintegrated at each pixel in the array of pixels 22. In some embodiments,the converter 70 and silicon detecting layer 67 include a fiber opticwith scintillator. In some embodiments, the array of pixels 22 convertsx-rays directly to charge without an intermediate step of convertingx-ray to light. In such embodiments, among other possible alterations,an additional insulator (similar to insulator 60) is positioned in placeof converter 70, and is used to provide electrical isolation between thehousing 45 and the PCB 65 and help transfer heat away from the PCB 65.

FIG. 3 depicts a cross section of the sensor 20 along line A as shown inFIG. 4. The top portion 50 is secured to the bottom portion 55 forinstance, using ultrasonic welding and machining. The welding bonds thetop portion 50 to the bottom portion 55, and machining smoothes thesurface. Additionally, the top portion 50 and bottom portion 55 includeinterlocking portions 56. The converter 70, PCB 65, silicon detectinglayer 67, and insulator 60 are shown within the housing 45. Alsodepicted is the cable 27 including stress relief portion 77. The stressrelief portion 77 is secured to the cable 27, for instance, using anadhesive. Additionally, the stress relief portion 77 includes acircumferential notch 80 that matches up with ridge 85 on the dome 75.The stress relief portion 77 is secured to the dome 75 using theinterlocking notch 80 and ridge 85. An adhesive may also be used tosecure stress relief portion 77 to the dome 75. The stress reliefportion 77 alleviates mechanical stress on the cable-to-housing coupling81 created from twisting, pulling, and other forces on cable 27 andhousing 45. Thus, the stress relief portion 77 extends the life of thecable-to-housing coupling 81, preventing or delaying malfunction of thesensor 20 caused by breaking the connection between the cable 27 and thehousing 45. FIG. 4 depicts a top view of the sensor 20 and a USBconnector 82 at the end of cable 27.

FIG. 5a depicts a cross section of a standard universal serial bus (USB)cable 100 capable of high speed USB version 2.0 communication. Thestandard USB cable 100 includes four main wires: data line 105 (D+),data line 110 (D−), power line 115, and ground line 120. Additionally,surrounding the four main wires is an isolating jacket 125, an outershield 130 made of 65% interwoven tinned copper braid, and an innershield 135 made of aluminum metallized polyester. The isolating jacket125 is made of polyvinyl chloride (PVC) in some embodiments. Runninglengthwise along with wire between the inner shield 135 and the outershield 130 is a copper drain wire 140. The standard USB cable 100 is notsymmetrical. Rather, the standard USB cable 100 has an internal,non-circular, oval structure, although fillers and plastic (not shown)may be used to create an external, circular shape of the cable. Theexternal, circular shape can be approximately 4 mm in diameter.

FIG. 5b depicts a wiring diagram of the standard USB cable 100. Asillustrated, the standard USB cable 100 has one twisted signaling pairincluding the data line 105 (D+) and data line 110 (D−). In someimplementations, the power line 115 and ground line 120 are twisted(possibly to a lesser extent) or, as shown in FIG. 5b , not twisted atall.

FIG. 6a depicts a cross section of a cable 150 according to embodimentsof the invention. The cable 150 includes four main wires 210 and fourfillers 175 a-d. The four main wires 210 include data line 155 (D+),data line 160 (D−), power line 165, and ground line 170, which providedata transmission, power transmission, and grounding, respectively. Thedata line 155 (D+), data line 160 (D−), power line 165, and ground line170 each include a metal conductor encapsulated by a co-axial insulator.The four fillers 175 a-d are made of plastic and are twisted along withthe four main wires 210 to form a twisted quad cable. The four mainswires 210 and four fillers 175 a-d are surrounded by three layers thatrun the length of the cable 150. The three layers includepolytetrafluoroethylene (“PTFE”) tape 180, a braided shield 185, and apolyurethane jacket 190. In some embodiments, other materials are usedfor the jacket 190 and the tape 180 (e.g., another material similar toPTFE with a low surface roughness). The braided shield 185 is made upof, for instance, tinned copper wires with 0.08 mm diameter (40 AWG). Aswill be discussed further below, in some embodiments, the braided shield185 is a heat conductor. In some embodiments, the polyurethane jacket190 is approximately 0.432 mm thick. The total diameter of the cable 150is less than 3.0 mm. In some embodiments, additional or fewer layerssurround the four main wires 210 and fillers 175 a-d used within cable27.

The wiring diagram of FIG. 6b illustrates the main wires 210 and fillers175 a-d twisted together to form a single bundle 195. Although not shownin FIG. 6b , the (“PTFE”) tape 180, a braided shield 185, and apolyurethane jacket 190 encapsulate the single bundle 195 as shown inFIG. 6a . The twisted quad cable is symmetrical about center line 197,as shown in FIG. 6 a. The symmetrical characteristic of the cable 150provides increased strength and resistance to mechanical stress with alower outside diameter, relative to the standard USB cable. That is, thecable 150 is less susceptible to damage from twisting, pulling, andother forces on the cable 150, despite the reduced diameter of the cable150. In particular, the cable 150 is less susceptible to damage due torotational mechanical stress, which is often present during use of anintraoral sensor cable.

FIG. 7 depicts the inside 200 of the top portion 50. The inside 200includes a metallization layer 205. The cable 27 is shown inserted intothe dome 75. The four main wires 210 (i.e., the data line 155 (D+), dataline 160 (D−), power line 165, and ground line 170) are attached to aPCB connector 215, which is connected to the PCB 65. In someembodiments, the four main wires 210 are coupled or soldered directly tothe PCB 65. The braided shield 185 is coupled to the metallization layer205 via a heat conducting wire 220. The heat conducting wire 220 iscoupled to the braided shield 185 and metallization layer 205 by, forinstance, soldering.

As the PCB 65 generates heat while in operation, a substantial portionof the generated heat is transferred through the insulator 60 to themetallization layer 205. The portion of generated heat is thentransferred to the braided shield 185 via the heat conducting wire 220.The level of thermal resistance may vary by application. For instance,the more heat the PCB 65 generates in a particular embodiment, the lowerthe thermal resistances are of the materials chosen for themetallization layer 205, heat conducting wire 220, and insulator 60. Ingeneral, however, the insulator 60 and heat conducting wire 220 have athermal resistance that is lower than the thermal resistance of air(which is approximately 1/0.025 W/(mK) at 20 degrees Celsius).Additionally, the metallization layer 205 has a thermal resistance thatis less than the thermal resistance of the top portion 50 of the housing45 and less than the thermal resistance of air. Thus, the sensor 20provides improved heat transfer away from the sensor 20 along the cable27.

Although not shown, in some embodiments the inside of the bottom portion55 also includes a metallization layer, which is similar to themetallization layer 205 in form and function. The bottom metallizationlayer is coupled to the braided shield 185 as well. In some embodiments,the coupling is provided by an additional heat conductor connectionbetween the bottom metallization layer and either the braided shield 185or the metallization layer 205. In other embodiments, the coupling isprovided by direct contact between the bottom metallization layer andthe metallization layer 205.

Thus, the invention provides, among other things, an intraoral sensorwith a cable providing greater resistance to mechanical stress.Additionally, the invention provides an intraoral sensor with improvedheat transfer. Various features and advantages of the invention are setforth in the following claims.

What is claimed is:
 1. An intraoral x-ray sensor comprising: a sensorhousing having an opening; and a universal serial bus (USB) data cableincluding an outer sheath, and a first data line, a second data line, aground line, a power line, and at least two independent fillerspositioned within the outer sheath, wherein at least two lines selectedfrom the group consisting of the first data line, the second data line,the ground line, and the power line, are twisted together to form asingle bundle, wherein the opening is configured to receive the datacable.
 2. The intraoral sensor of claim 1, wherein the first data line,the second data line, the ground line, the power line, and theindependent fillers are symmetrically organized about a centerline ofthe data cable.
 3. The intraoral sensor of claim 2, wherein the firstdata line abuts the second data line at a center of the cross-section ofthe data cable.
 4. The intraoral sensor of claim 1, wherein theindependent fillers comprise a plastic, electrically insulatingmaterial.
 5. The intraoral sensor of claim 1, wherein the independentfillers include a first filler, a second filler, a third filler, and afourth filler, and wherein the first filler abuts the ground line andthe first data line, the second filler abuts the ground line and thesecond data line, the third filler abuts the power line and the firstdata line, and the fourth filler abuts the power line and the seconddata line.
 6. The intraoral sensor of claim 1, wherein the outer sheathfurther comprises a braided shield, a jacket layer outside of thebraided shield and a tape layer inside of the braided shield.
 7. Theintraoral sensor of claim 1, wherein the data cable has a diameter ofless than 3.0 millimeters.
 8. The intraoral sensor of claim 1, whereinone end of the data cable is coupled to an x-ray sensor.
 9. Theintraoral sensor of claim 1, wherein the cable further comprises astress relief portion.
 10. The intraoral sensor of claim 1, wherein thehousing further comprises a dome and the dome is configured to receivethe cable.
 11. The intraoral sensor of claim 10, wherein the cablefurther comprises a stress relief portion.
 12. The intraoral sensor ofclaim 1, wherein the housing further comprises a dome and the dome isconfigured to receive the cable, and the cable further comprises astress relief portion and the stress relief portion is secured to thedome.